A droplet actuator typically includes one or more substrates configured to form a surface or gap for conducting droplet operations. The one or more substrates establish a droplet operations surface or gap for conducting droplet operations and may also include electrodes arrange to conduct the droplet operations. The droplet operations substrate or the gap between the substrates may be coated or filled with a filler fluid that is immiscible with the liquid that forms the droplets. It may be beneficial to determine and/or verify the presence or absence of liquid at certain electrodes of a droplet actuator, such as at droplet operations electrodes and reservoir electrodes. Therefore, there is a need for methods of microfluidic feedback in droplet actuators.